Predatory bacteria attack in 'military-style' waves

A soil bacteria like M. xanthus executes a wave-like 'military-style' attack in a swarm against their prey, before gobbling them up and moving on.

Despite its deadly role, M. xanthus is harmless to humans and might be used to destroy harmful bacteria on surfaces or in human infections, said John Kirby, associate professor of microbiology at the University of Iowa (U-I) Carver College of Medicine.

"When an M. xanthus aggregate is placed inside a colony of E. coli bacteria," it "proceeds to eat the colony from the inside out and creates a rippling pattern as the swarm moves through the prey cells," Kirby said.

"We now know that this rippling pattern is the highly organised behaviour of thousands of cells working in concert to digest the prey."

"It may be that we can modify this predator-prey relationship or apply it to medically relevant situations," Kirby said. "It would be amazing if we could adapt its predatory ability to get rid of harmful bacteria that reside in places we don't want them, including in hospitals or on medical implants."

The U-I team also showed that the ripple wavelength is adaptable. At high prey density, M. xanthus forms ripples with shorter wavelengths. As prey density decreases, the ripple wavelength gets longer. Eventually, when there is no more prey, the rippling behaviour dissipates.

M. xanthus lives in a multi-cellular unit that can change its structure and behaviour in response to changing availability of prey. This adaptive ability to control movement in response to an environmental stimulus is called chemotaxis, and the research team coined the term predataxis to describe its behaviour in response to prey, said a U-I press release.

These findings were published online in the Proceedings of the National Academy of Sciences (PNAS) early edition.

In earlier studies, Kirby and James Berleman, postdoctoral fellow in Kirby's lab, showed that the presence of prey causes M. xanthus to form parallel rippling waves that move toward and through prey bacteria.

Now, how the bacteria organise to form these travelling waves in response to the presence of prey is the subject of the study.

Last updated on Oct 30^th, 2008 at 11:01 am IST--IANS